The present invention relates to methods and apparatus for carrying out non-invasive urodynamics investigations on male patients, and in particular to methods and apparatus for controlling urethral pressure and making measurements of bladder pressure, in order to, for example, facilitate diagnosis of, and distinction between, obstructive and non-obstructive voiding dysfunction.
In the past, urodynamics investigations have been carried out using invasive techniques using, for example, catheters introduced into the bladder. Such catheters can be used for both filling the bladder and directly measuring pressure within the bladder, allowing a comprehensive assessment to be made. However, such invasive techniques are associated with severe patient discomfort, a degree of morbidity, and high cost both in financial terms and in time.
It is found that a proportion of men undergoing prostatectomy do not get the anticipated benefit therefrom and many urologists believe all men should have a urodynamics study beforehand to help identify those less likely to benefit from surgery. There is a real need for a simple, easily administered, atraumatic test which will provide information similar to that currently only available from a full urodynamics study, to give objective evidence of obstruction.
A number of prior art techniques have been proposed for non-invasive measurements on male patients. Many of these suggest the use of a condom catheter, having a stop valve and pressure measurement port, which fits over the penis and can be used to make pressure and flow rate measurements under xe2x80x9cinterrupted flowxe2x80x9d or isovolumetric conditions. Such devices are often associated with problems of erroneous measurements arising from leakage and distortion or high compliance of the device, and can be awkward and messy to use.
In another prior art approach, as described in Neurourology and Urodynamics 14:101-114 (1995) xe2x80x9cNon-invasive Quantitative Method for Measuring Isovolumetric Bladder Pressure and Urethral Resisance in the Malexe2x80x9d, L P McRae et al, it has been suggested to use an inflatable cuff around the penis which is initially pressurised to occlude the urethra. The patient then attempts to void so that the urethra above the occluding cuff becomes distended with urine and the static intraurethral pressure proximal to the cuff is related to the maximum isovolumetric bladder pressure. The cuff is then gradually deflated until urinary flow commences, at which point the cuff is rapidly deflated to enable volume and flow rates to be measured. Cuff pressure at the point of first urine passage can be used to assess isovolumetric bladder pressure at the commencement of voiding. No further estimate of bladder pressure is made during the subsequent voiding cycle.
Such a technique can be susceptible to a number of disadvantages. Only a single estimate of bladder contraction is made, which is at the start of the voiding cycle and is based on the occurrence of an event which can be unreliable. No further measurements are obtained to assess how well the bladder contraction is sustained during the rest of the voiding cycle. The measurement is prone to false starts due to transient events such as straining and contraction of the external sphincter which might lead to an erroneous result. It will not always be apparent that this has occurred.
The cuff pressure must initially be elevated to a high level before. commencing the test. For many subjects, this may be higher than necessary and could cause problems.
Many patients with symptoms of obstruction can have hesitation and difficulty initiating voiding. This can make identification of the best time to start reducing the pressure difficult.
It is an object of the present invention to provide a method and apparatus. for carrying out urodynamics studies on male patients.
It is a further object of the present invention to provide a method and apparatus for carrying out a new type of urodynamics study on male patients which provides valuable information previously only available from catheterisation and a conventional urodynamics study, but achieving this with a well tolerated, easily repeated, quick to perform, non-invasive test.
It is a further object of the invention to provide a method and apparatus for obtaining measurements of flow rate during application of a controlled increase in pressure in a penile cuff leading to a reliable measurement of bladder isovolumetric contraction pressure or other rodynamics parameter. Preferably, this can be applied a number of times during the voiding cycle.
According to one aspect, the present invention provides a method of making urethral pressure measurements on a male body comprising the steps of: attaching a pneumatic cuff around the penis; after commencement of urine flow through the penis, automatically inflating the cuff over a period of time in order to gradually occlude the urethra before voiding of the bladder is complete; establishing a relationship between the urine flow and the, cuff pressure applied; and using said established relationship to determine a pressure measurement related to the urethral pressure under isovolumetric conditions.
According to another aspect, the present invention provides an apparatus for making urethral pressure measurements on a male body comprising: a pneumatic cuff adapted to fit around the penis; means for automatically inflating the cuff over a period of time during voiding of the bladder through the urethra in order to gradually occlude the urethra before voiding of the bladder is complete; and means for determining the cuff pressure at which the urethra becomes completely occluded.
According to another aspect, the present invention provides an apparatus for making urethral pressure measurements on a male body comprising: a pneumatic cuff adapted to fit around the penis; means for automatically inflating the cuff over a period of time during voiding of the bladder through the urethra in order to gradually occlude the urethra before voiding of the bladder is complete; means for recording volume of urine flow and cuff pressure as a function of time; means for establishing, from said means for recording, a relationship between urine flow rate and cuff pressure; and means for determining, from said relationship, information about the relationship between bladder contraction and outlet function. In a preferred arrangement, the information may include a measure of outflow resistance.
According to another aspect, the present invention provides an apparatus for making urethral pressure measurements on a male body comprising:
a pneumatic cuff adapted to fit around the penis; means for automatically inflating the cuff over a period of time during voiding of the bladder through the urethra in order to gradually occlude the urethra before voiding of the bladder is complete; means for recording volume of urine flow and cuff pressure as a function of time; means for establishing, from said means for recording, a relationship between urine flow rate and cuff pressure; and means for determining, from said relationship, a measurement related to at least one of: isovolumetric bladder pressure, a minimum value for the contraction pressure at maximum flow, and the opening pressure of a compressive flow controlling zone.
According to another general aspect, the present invention provides an apparatus for controlling urethral pressure on a male body comprising: a pneumatic cuff adapted to fit around the penis; means for automatically inflating the cuff over a period of time during voiding of the bladder through the urethra in order to gradually occlude the urethra before voiding of the bladder is complete; and means for determining the cuff pressure at which the urethra becomes completely occluded.